1. Field of the Invention
The present invention relates to a fluid heating apparatus for gas or liquid, for example, to a fluid heating apparatus, connected with various semiconductor heating treatment furnaces used in semiconductor manufacturing process, controlling temperature of gas supplied to the semiconductor heating treatment furnaces.
2. Description of the Related Art
In semiconductor manufacturing process, for example, in an impurity diffusion furnace, an oxidation furnace, an annealer, a thin film deposition system, an etching system and the like, various semiconductor heating treatment furnaces are used. In these semiconductor heating treatment furnaces, various types such as single wafer processing type, vertical type, horizontal batch processing type are present corresponding to object and use.
Conventional vertical batch processing oxidation reaction furnace will be described based on FIG. 12. This reaction furnace 60 is comprised of a reaction tube heating furnace 61, a liner tube 62 and a reaction tube 63 and constituted so that wafer boat (not shown) supporting wafer by multistage can be arranged in the reaction tube 63.
In such a reaction furnace 60, reacting gas is introduced from a reacting gas inlet 64 through a reacting gas nozzle 65 and a gas introducing section 66 provided in the reaction tube heating furnace 61 into the reaction tube 63.
In conventional vertical batch processing oxidation reaction furnace 60, reacting gas is pre-heated by heat of a heater (not shown) embedded in the reaction tube heating furnace via the liner tube 62 when passing through the gas introducing section 66, and temperature thereof rise.
However, temperature of reacting gas introduced from the external is low compared with that inside the reaction tube 63, and reacting gas is not heated enough, therefore temperature difference occurs, thereby partial pressure distribution of decomposition product gas of reacting gas in the reaction tube 63 become uneven.
As a result, there are abuse that reaction difference between wafers contained inside the reaction tube 63 is produced, thereby film thickness and quality of film become uneven which are generated in the wafers, therefore excellent oxide film can not be obtained.
As the method to solve above-mentioned abuse, it is suggested that reacting gas is heated to a predetermined temperature corresponding to a process temperature of the semiconductor heating furnace by a heating device before introduction into the furnace to uniform temperature distribution in the furnace (JP-A 63-316425, JP-A 7-176498).
A gas heating apparatus which heat-controls reacting gas to be introduced in a vertical reaction furnace to a predetermined temperature is disclosed in JP-A7-176498. Here, this gas heating apparatus will be described based on FIG. 13. This gas heating apparatus 70 is comprised of a heating path portion 73 formed in snake-like and a temperature uniformity matter (heating matter) 72 provided in the heating path portion 73, and constituted so that reacting gas introduced from a gas inlet 71 is heated by the temperature uniformity matter (heating matter) 72 of the gas heating apparatus to flow in the long narrow heating path portion 73 formed in snake-like to introduce into the furnace.
Here, the arrow in FIG. 13 shows the flow of reacting gas.
A gas heating apparatus which heat-controls reacting gas to be introduced into an epitaxial thin film vapor phase growth system using a single wafer processing furnace to predetermined temperature is disclosed in JP-A 63-316425.
Here, this gas heating apparatus will be described based on FIG. 14, FIG. 15. This gas heating apparatus 80 is comprised of a spiral tube 81 and a heater section 82 provided outside of the spiral tube 81, and constituted so that reacting gas is heated to predetermined temperature by heat from the heater section 82 while reacting gas is passed through the spiral tube 81, and then reacting gas is supplied from a nozzle 83 to a belljar 84. Here, the arrow in FIG. 14, FIG. 15 shows the flow of reacting gas.
In the case where the gas heating apparatus disclosed in JP-A 7-176498 is applied to a oxidation furnace, if the heating path portion is made of high purity quartz tube, the temperature uniformity matter (heating matter) is made of heating element made of high purity silica carbide (SiC), since vapor (H2O) is used as reacting gas, and oxygen is entered into inside of SiC heating element to produce internal oxidation, thereby structural degradation and particle are generated, which has been problems.
And when hydrogen is flow in annealer, impurity gas is generated by reaction between SiC heating element and hydrogen, which has been a problem.
Furthermore, SiC heating element has large heat capacity and bad heat response, therefore rapid rise and fall of temperature is impossible.
In the gas heating apparatus disclosed in JP-A 63-316425, the apparatus is constituted so that reacting gas is passed through the spiral tube, however, gas is difficult to stay, if the length of the spiral tube is extended, reacting gas may be heated to predetermined temperature. On the other hand, when the length of the spiral tube is extended in order to heat gas to predetermined temperature, the gas heating apparatus can not be miniaturized.
The present invention is developed to solve the technological problems described above, it is an object of the present invention to provide a fluid heating apparatus which can improve durability, suppress generation of particle and the like or metallic contamination and the like and be miniaturized.
The fluid heating apparatus, in accordance with the present invention, developed to solve the technological problems described above is characterized by comprising at least a heating tube heating fluid to be supplied from fluid supply source, a heater section spirally formed on an outer periphery of the heating tube and a housing accommodating the heating tube and the heater section, wherein the heater section comprises a carbon wire heating element and a quartz glass tube in which the carbon wire heating element is enclosed.
The constitution of the fluid heating apparatus in accordance with the present invention is characterized in that the heater section comprises a carbon wire heating element and a quartz glass tube in which the carbon wire heating element is enclosed, and the heater section is spirally formed on an outer periphery of the heating tube.
This way, heat capacity of the heater section comprising the carbon wire heating element enclosed in the quartz glass tube is small compared to a conventional heater made of high purity SiC, and there is a small amount of generation of metallic contamination, particle and impurity gas harmful to semiconductor wafer.
Furthermore, heating efficiency and heat responsiveness in temperature rising operation of fluid are excellent because the heater section is spirally formed on the outer periphery of the heating tube, heating the fluid.
In addition, it is preferable that the fluid heating apparatus in accordance with the present invention is used as gas heating apparatus for heat controlling gas to be introduced in the semiconductor treatment furnace in the case where fluid is gas. Thus, it is more preferable that the fluid heating apparatus in accordance with the present invention is constituted as the heating apparatus, connected with a gas supply source and the semiconductor treatment furnace, comprising at least a heating tube heating gas to be supplied from gas supply source, a heater section spirally formed on an outer periphery of the heating tube and a housing accommodating the heating tube and the heater section, wherein the heater section comprises a carbon wire heating element and a quartz glass tube in which the carbon wire heating element is enclosed. This reduces variation in treatment temperature in the semiconductor treatment furnace and impurity contamination of the semiconductor wafer to be gas treated.
Here, it is desirable that filling which act as resistance for passing fluid is arranged inside the heating tube.
This way, suitable residence time can be added to passing fluid because filling which act as resistance for passing gas, for example, is arranged inside the heating tube.
As a result, fluid which pass inside the heating tube can obtain enough heat by radiation heat from the carbon wire heating element, which can rise temperature to a predetermined temperature. And the heating tube and the heater section can be miniaturized because it is possible to stay fluid passing inside the heating tube.
In addition, it is desirable that the filling comprises a molded matter formed by welding short column-like quartz glass beads or a porous quartz glass molded matter in which communicated pore is formed.
Particularly, it is desirable that the molded matter which are formed by welding short column-like quartz glass beads is the molded matter formed by mixing large and small, two kinds of beads having a diameter of 6 to 12 mm and a length of 6 to 12 mm and breads having a diameter of 4 to 10 mm and a length of 4 to 10 mm at the number ratio of 1:4 to 4:1 (more preferably at the ration of 6:4 to 8:2) to weld.
This way, since filling comprising the molded matter formed by welding quartz glass beads or the porous quartz glass molded matter in which communicated pore is formed is arranged in the heating tube, suitable residence time is added by passage of gas introduced into the heating tube through fine pass, formed by filling, complicatedly distortedly intersected. In addition, radiation heat from the carbon wire heating element complicatedly repeat transmission, refraction, scattering, reflection inside the molded matter.
As a result, heat exchange efficiency may be improved, and the heating tube and the heater section may be miniaturized because enough quantity of heat may be added to introduced gas.
In addition, a large part of heat energy transmitted from the carbon wire heating element of the heater section into the heating tube is radiation heat because heat conductance of quartz matter such as quartz glass is not large. Therefore, it is preferable that filling inside the heating tube is transparent matter rather than black matter.
Because in the case of black matter, radiation is absorbed at the part of surface of black matter, thereby only the surface part is partially heated. On the other hand, in the case of transparent matter, radiation heat irradiated to transparent matter complicatedly transmit, reflect and refract to reach the center portion, thereby the inside of filling may be heated uniformly, and gas which pass through inside of the heating tube may be heated uniformly. Accordingly, it is preferable that quartz glass beads which is filling is comprised of transparent quartz glass.
It is also preferable that the filling is a plurality of quartz glass pipes or a gas disturbing plate, made of quartz glass, having a plurality of opening sections. In particular, it is desirable that a plurality of gas disturbing plates are accommodated inside the heating tube, and that plates are constituted so that opening sections of neighboring gas disturbing plates are not corresponded to each other at least.
The same effect as filling described above may be obtained even if such filling.
In addition, it is desirable that high purity heat insulating material is filled in space between the heater section and the housing.
Because heat insulating material is filled in the space, a fluid heating apparatus whose heat insulation properties, shading properties and heating efficiency are excellent may be obtained.
And it is desirable that the heating tube and the heater section are accommodated in a thermal shield provided in the housing. In particular, it is desirable that the thermal shield is cylindrical, and a reflecting heat insulating coat film including silica fine powder and alumina fine powder is formed at least inside surface thereof. In order to obtain a thermal shield effectiveness of this thermal shield, it is preferable to form a reflecting heat insulating coat film on the inside surface thereof. This way, because the heating tube and the heater section are accommodated in the thermal shield, made of quartz glass, provided in the housing, a fluid heating apparatus whose heat insulation properties, shading properties and heating efficiency are excellent may be obtained.
In particular, in the case where a reflecting heat insulating coat film including silica fine powder and alumina fine powder is formed inside surface of the thermal shield, not only excellent heat insulation properties and shading properties but also ability to trap impurity on the surface thereof may be obtained.
Furthermore, it is desirable that compounding ratio between silica fine powder and alumina fine powder of the reflecting heat insulating coat film is a parts by capacity of 3:1 to 3:7, and the coat film further includes titanium oxide fine powder.
Compounding ratio between silica fine powder and alumina fine powder is less than parts by capacity of 3:7, and if ratio of silica fine powder become small, ability to trap impurity on the surface of the film is reduced.
On the other hand, compounding ratio between silica fine powder and alumina fine powder is more than parts by capacity of 3:1, and if ratio of alumina fine powder become small, an abuse that surface crack and peeling in forming the coat film are easy to occur, arises because silica fine powder is too much.
And it is desirable that film thickness of the reflecting heat insulating coat film is within the range of 30 to 300 xcexcm. When the thickness of the reflecting heat insulating coat film is less than 30 xcexcm, heat insulation properties and shading properties become worse, and when that is more than 300 xcexcm, layer-like crack is easy to occur on the coat film, thereby abuse that the coat film is easy to peel arises.
In addition, it is desirable that high purity heat insulating material is filled in space between thermal shield and the housing.
Because high purity heat insulating material is filled in space between thermal shield and the housing, a fluid heating apparatus whose heat insulation properties, shading properties and heating efficiency are excellent may be obtained.
And, in the present invention, the apparatus may be more miniaturized by constituting the housing itself by high purity heat insulating material.
And it is desirable that the carbon wire heating element is a knitted cord-like or braid-like carbon wire heating element comprising a plurality of fiber bundle wherein carbon fiber having a diameter of 5 to 15 xcexcm is bundled braided. And it is desirable that included impurity quantity of carbon fiber in the carbon wire heating element is not more than 10 ppm as ash content.
This way, in the case where carbon wire heating element is formed in knitted cord-like or braid-like, tensile strength is high, durability in high temperature is excellent and the heating element may be deformed easily, thereby this heating element may be easily accommodated inside spiral shaped quartz glass tube constituting the heater section.
Furthermore, diffusion of impurity may be prevented because included impurity quantity of carbon fiber constituting the carbon wire heating element is not more than 10 ppm as ash content, which is high purity.
The fluid heating apparatus in accordance with the present invention, is characterized by comprising at least a heating tube heating fluid to be supplied from fluid supply source, a heater section spirally formed on an outer periphery of the heating tube and a housing accommodating the heating tube and the heater section, wherein the heater section comprises a carbon wire heating element and a quartz glass tube in which the carbon wire heating element is enclosed, and a porous molded matter formed by partially welding a plurality of quartz glass beads is arranged inside the heating tube.
Since such porous molded matter is arranged inside the heating tube, suitable residence time is added by passage of gas introduced into the heating tube through fine pass, formed by filling, complicatedly distortedly intersected. And radiation heat from the carbon wire heating element complicatedly repeat transmission, refraction, scattering, reflection inside molded matter.
As a result, heat exchange efficiency may be improved, and the heating tube and the heater section may be miniaturized because enough quantity of heat may be added to introduced gas.
In addition, quartz glass beads in the invention comprise various form such as column-like matter, spherical matter, rectangular parallelepiped matter comprising quartz glass or pipe-like matter, comprising quartz glass, in which hollow portion is formed. And the size of quartz glass beads is not limited particularly, if molded matter on which a plurality of quartz glass beads is welded may be formed in the heating tube.
Here it is desirable that the carbon wire heating element is a knitted cord-like or braid-like carbon wire heating element comprising a plurality of fiber bundle wherein carbon fiber having a diameter of 5 to 15 xcexcm is bundled braided. And it is desirable that included impurity quantity of carbon fiber in the carbon wire heating element is not more than 10 ppm as ash content.
This way, in the case where carbon wire heating element is formed in knitted cord-like or braid-like, tensile strength is high, durability in high temperature is excellent and the heating element may be deformed easily, thereby this heating element may be easily accommodated inside spiral quartz glass tube constituting the heater section, thereby it becomes possible to make the heater section of this fluid heating apparatus design and arrange on an outer periphery portion of the heating tube with high accuracy.
Furthermore, diffusion of impurity may be prevented because included impurity quantity of carbon fiber constituting the carbon wire heating element is not more than 10 ppm as ash content, which is high purity.
Also, it is preferable that the heating tube and the heater section are accommodated in high purity heat insulating material provided in the housing. This causes heat efficiency to improve, and it becomes possible to miniaturize the housing.